PROJECT SUMMARY Exposure to childhood maltreatment is one of the most powerful predictors of poor mental health outcomes in adolescence and adulthood, increasing risk for nearly all commonly occurring forms of psychopathology. Many children who experience early abuse and/or neglect are removed from their families of origin and placed in foster or kinship care, which exacerbates experiences of stress and instability. Given that stress exposure compounds pre-existing risk for psychopathology, and that rates of internalizing and externalizing disorders significantly increase during adolescence, understanding how victims of childhood maltreatment respond to psychosocial stress during adolescence is vital to enhance early intervention and prevention efforts. This study aims to identify and integrate findings on the biological and psychological responses to stress that are unique to adolescents with a history of maltreatment. The two mechanisms of interest are physiological reactivity to stress, including arousal of the sympathetic (SNS) and parasympathetic (PNS) branches of the autonomic nervous system (ANS), and coping, which refers to conscious efforts to respond to stressful events or circumstances and includes the regulation of emotions. Previous studies have established broad deficits in these processes associated with early abuse and neglect; however, findings on stress reactivity patterns have been mixed, the specific coping strategies employed by maltreated youth are unclear, and examination of the interplay between these constructs remains open for investigation. The proposed research will generate initial findings on the relation between early trauma and specific deficits in the stress response system in young adolescents, ages 10-15, who have experienced early-life maltreatment. Three main aims are proposed. [Aim 1: Test group differences in coping/emotion regulation (ER) strategies and patterns of physiological stress reactivity in maltreated and never-maltreated adolescents, integrating measurement of both branches of the ANS system by assessing skin conductance level (SNS index) and respiratory sinus arrhythmia (PNS index). Aim 2: Examine the concurrent associations between physiological reactivity and coping/ER in response to stress. Aim 3: Test ANS reactivity and coping/ER, as well as the interaction of these terms, as potential mediators in the relationship between early-life maltreatment and later symptoms of psychopathology.] This study employs multiple methodologies, including questionnaires, interviews, physiological measurement, and observational paradigms, allowing for a comprehensive assessment of the proposed hypotheses. Training tied to this proposal will enhance skills in assessment (e.g., physiological data collection, clinical interview methods, and stress-induction tasks), [advanced data analysis (e.g., regression and mediation model implementation),] and scientific professional development (e.g., publication preparation, grant management, and cross-site collaboration experience). Together, this research and training will prepare me for a productive career as a clinical investigator of early trauma and associated risk factors.